U.S. health regulators are seeking a second opinion on whether dental fillings containing mercury pose a risk to dental patients, especially children and pregnant women.

Food and Drug Administration officials said that while there are no new scientific findings on such silver-colored cavity fillings, it wants feedback on methods it used to weigh available data and decide last year that the metal alloy is safe.

In documents released on Friday ahead of a public meeting on the issue, the agency said it would ask its panel of outside experts to asses how much mercury dental patients are exposed to and how much exposure is acceptable.

The FDA reversed course in July 2009 and declared the fillings, known as dental amalgam, posed no risk. Earlier, it cautioned against their use in certain more vulnerable people such as pregnant women and children.

The agency is revisiting the issue after four groups questioned its assessment and petitioned for a second look. On Tuesday and Wednesday next week, the panel of outside experts will consider available data as well as the agency's interpretation before offering recommendations.

"Based on its own review and feedback from the panel, FDA will decide whether to make changes to its regulation," Nancy Stade, deputy director of policy for the FDA's device center, told reporters on Thursday. "At this time, the FDA is not modifying its existing recommendations to consumers."

Millions of Americans have had cavities in their teeth patched with the lower-cost dental amalgam. Other options include bone-colored resin.

FDA could decide to continue backing the metal fillings, again urge more cautious use, or ban the products.

Mercury is a known toxin. At issue is whether the vapors released from mercury in dental fillings are enough to cause harm such as brain or kidney damage.

While some experts and advocacy groups say mounting data show a clear link between mercury and side effects, and that dental fillings are no exception, industry groups and dentists say the evidence shows dental amalgam is safe.